The present invention generally relates to liquid heating apparatus and, in a representatively illustrated embodiment thereof, more particularly relates to a storage type water heater having incorporated therein a specially designed control algorithm that reduces undesirable temperature stratification in the water heater and improves its energy factor.
As conventionally manufactured, a storage type water heater, whether of a fuel-fired or electric heating apparatus type, has an insulated tank for storing heated water for on-demand delivery to various plumbing fixtures such as sinks, bath tube, showers, dishwashers and the like. The water stored in the tank is heated by heating apparatus in the form of a fuel burner or one or more electrical resistance type heating elements operated by a thermostatic control system in response to a sensed temperature of the tank water falling below a predetermined setpoint temperature.
A problem commonly associated with such fuel-fired or electrically heated storage type water heaters is that of thermal stratification or “stacking” in which stored water in an upper end portion of the tank reaches significantly higher temperatures than the setpoint temperature. Since supply water from the tank is typically drawn from the upper end of the tank, a stacking condition in the tank can lead to hot water delivered to a user from the tank being at a substantially higher temperature than anticipated Additionally, this stacking effect may undesirably increase stand-by losses associated with the water heater.
It can therefore be seen that it would be desirable to provide a fuel-fired or electrically heated storage type water heater in which both stacking and related reduction in the water heater energy factor are diminished. It is to this goal that the present invention is primarily directed.